Patches to be applied to the skin for the purpose of, e.g., protecting the affected part and adhesive preparations to be applied to a surface of the skin of a mammal for the purpose of percutaneously administering a drug to the mammal have hitherto been developed. Recently, soft pressure-sensitive adhesive layers such as those holding a large amount of a liquid component therein tend to be employed for the purpose of obtaining a soft wear feeling during wear of the patch or reducing the skin irritation caused by separation of the horny layer upon stripping of the patch. With regard to adhesive preparations in which the pressure-sensitive adhesive layer contains a drug, a pressure-sensitive adhesive layer having a larger thickness is frequently employed in recent adhesive preparations so that the pressure-sensitive adhesive layer holds a large amount of a drug. In such a case, there may arise a trouble that the pressure-sensitive adhesive layer protrudes from an edge of the patch during storage and adheres to the inner surfaces of the package, whereby it becomes difficult to take out the patch out of the package. This tendency is significant when the pressure-sensitive adhesive layer is thick, since the amount of the pressure-sensitive adhesive layer is large.
Various proposals have been made in order to overcome those problems. For example, JP-T-10-511330 (herein, the term “JP-T” as used herein means a published Japanese translation of a PCT patent application) discloses a package for disposing therein a patch to be applied to the skin (in this document, the structure composed of a pressure-sensitive adhesive layer and a backing excluding a release liner is referred to as “patch”). An example of this package is shown in FIG. 8.
This package is constituted of a blister pack 12 in a container form and a cap 14 in a sheet form, and a patch 1 is disposed in this package. In this package, the blister pack 12 in a container form has a central part 18 which is almost flat and horizontal and a peripheral outer part 22 which is deeper than the central part. The patch 1 has been attached to a release liner 3 larger than the patch. Owing to such a shape of the blister pack and the large release liner, peripheral parts of the patch 1 do not come into contact with any part of the package. There is a statement therein to the effect that the pressure-sensitive adhesive can be thus prevented from leaking out through the peripheral parts or lower side (release liner side) of the patch 1 and thereby bonding the patch 1 to the package.
However, since the blister pack 12 of this package is in the form of a container, the package as a whole becomes thick. Accordingly, the overall volume of this package becomes far larger than the patch itself. Consequently, this package is not fully satisfactory from the standpoints of the production cost thereof and the cost of handling including the transportation of packaged products.
An Example given in that document teaches that the constitution including an outer wall 24 having a substantially vertical upper region and the like enhance the overall strength of the package 10. However, the package described in this Example is thick as a whole as well as the angle formed by the outer wall 24 and the flange 26 in the blister pack (rising angle) is almost an right angle. Therefore, this package has such a drawback that, when the package is opened by cutting from the sealed part to the blister pack with scissors, a considerable power is necessary for the scissoring and, as a result, there is a possibility that the patch placed therein might be accidentally cut together with the package or, in the worst case, the scissors might injure the hand.
Furthermore, a laminated packaging material obtained by laminating sheet materials may be used as the material of the blister pack. In this case, there is a possibility that, when a blister pack having such a substantially right-angled bent part is molded from the sheet-form laminate packaging material, the blister pack thus obtained might suffer laminate failures such as delamination at the bent part. Especially in the case of a packaging material including an aluminum foil, there is a possibility that the aluminum foil might crack or otherwise break. In such a case, there is a possibility that the package structure might be impaired in impermeability to the package contents such as a drug, or in impermeability to light rays or gases, resulting in impaired quality stability of the package contents.
In this document, there is a statement to the effect that the depth (gap distance) of the central part of the blister pack from the cap is sufficiently larger than the total thickness of the patch and the release liner so that the patch and the release liner can move freely, whereby the patch is prevented from being pressed and the pressure-sensitive adhesive is hence prevented from being squeezed out from the downside of the patch (on the release liner side). There also is a statement to the effect that the outer part of the blister pack should also have a sufficient depth in order to prevent the pressure-sensitive adhesive from leaking out through edges of the patch and then coming into contact with the bottom of the blister pack. As described above, this document does not suggest a thin package structure.
On the other hand, a patch package structure obtained without using a so-called blister pack has been conventionally utilized. It is produced by sandwiching a patch between two pieces of flexible sheet-form packaging materials having a slightly larger planar outer shape than the patch and then sealing the two pieces of flexible sheet-form packaging materials together in peripheral parts thereof. For example, JP-UM-B-4-51782 discloses a bag container obtained by sealing two pieces of planar sheet materials together in peripheral parts thereof, and an example of the bag container is shown in FIG. 9. However, since such a bag container is constituted of two pieces of planar flexible sheet materials, it has the following drawback. Namely, since a load is apt to be imposed on the patch in the thickness direction therefor and the patch freely moves in the bag container, the pressure-sensitive adhesive layer protruded from peripheral parts of the patch comes into contact with the inner surfaces of the bag container and the components of the pressure-sensitive adhesive layer thus adhere to the inner surfaces of the bag container, whereby it often becomes difficult to take out the patch out of the bag container. This tendency is significant especially when the pressure-sensitive adhesive layer contains a large amount of a liquid component or the pressure-sensitive adhesive layer is soft or thick.
Under such circumstances that a pressure-sensitive adhesive layer containing a large amount of a liquid component, a soft pressure-sensitive adhesive layer, or a thick pressure-sensitive adhesive layer is employed, a technique for preventing components of the pressure-sensitive adhesive layer of a patch from adhering to the inner surfaces of the package to thereby secure the ease of taking the patch out of the package has become increasingly important in recent years.